1. Field of the Invention
The present invention relates to an adaptive control apparatus that electrically and adaptively controls an antenna directional pattern by controlling weighting coefficients for radio signals received through a plurality of antennas, according to a propagation environment, and relates to a wireless communication apparatus including the adaptive control apparatus.
2. Description of the Related Art
In Patent Document 1, for example, an adaptive control apparatus for avoiding the misconvergence and improving the convergence rate is provided. In this adaptive control apparatus, a plurality of algorithm units compute ratios of combinations of signals received through a plurality of antennas, SIR calculating sections respectively compute SIR values of combined signals which are obtained by combining the signals at the computed ratios of combinations, a determination unit determines which algorithm unit yields the combined signal with the highest quality, and a selection unit selects the combined signal with the highest quality as a received signal. As such, among combined signals obtained by different algorithms, the combined signal having the highest quality is selected as the received signal, and accordingly, even when the computation of weighting coefficients by any of the algorithms becomes unstable or is misconverged for some reason, a combined signal obtained by this algorithm is not selected, but a combined signal obtained by another algorithm is selected. Thus, the computation of weighting coefficients can continue in a stable manner, and a misconvergence can be avoided.
Furthermore, a combining ratio computed by an algorithm with a fast convergence rate is used as an initial value of an algorithm with a slow convergence rate. Accordingly, weighting coefficients computed by a first algorithm unit, which has poor interference wave removal characteristics but has a fast convergence rate, are used as initial values for other second or third algorithm unit, thus improving the convergence rate of the second or third algorithm unit.
Thus, according to the prior art adaptive control apparatus, an adaptive control apparatus can be provided that is capable of avoiding a misconvergence by selecting, as a received signal, a combined signal with the highest quality from among computation results obtained by a plurality of algorithms, and capable of improving a convergence rate by using a combining ratio computed by an algorithm with a fast convergence rate, as an initial value of an algorithm with a slow convergence rate.
Patent Document 1: PCT International Publication WO 02/047289 (FIG. 3).
Non-Patent Document 1: Nobuyoshi KIKUMA, “Adaptive Signal Processing with Array Antenna”, Kagaku Gijutsu Shuppan, Inc., pp. 125-137, Nov. 25, 1998.
Non-Patent Document 2: Yoshio KARASAWA, “Fundamentals of Radio Wave Propagations for Digital Mobile Communications”, Corona Publishing Co.,Ltd., pp. 55-56, March 2003.